1. Field of the Invention
The present invention pertains generally to apparatus for controlling the voltage applied to a load for purposes of conserving power and more specifically, to an improved transformer apparatus for advantageously lowering the voltage applied to a load such as a bank of fluorescent lights after initial turn on of such lights.
2. Prior Art
The present invention is particularly suited to the function of permitting the application of a normal high voltage to a lighting load such as a bank of fluorescent lights and to thereafter, selectively reducing the voltage to maintain such lights in a lighted condition but with reduced power consumption. The general concept of voltage reduction for the aforementioned purpose is well-known in the art. By way of example, U.S. Pat. No. 2,429,162 issued Oct. 14, 1947 to Kaiser et al discloses a number of alternative transformer configurations utilizing a variety of switches and relays. These configurations permit the application of a nominal voltage to a plurality of fluorescent lamps followed by a reduction in that voltage subsequent to lamp lighting in order to maintain the lamps in a lighted condition at a reduced power consumption. A more recent patent, No. 4,189,664 issued Feb. 19, 1980 to Hirschfeld, discloses another type of transformer configuration utilizing a switch for selectively applying one of a plurality of taps from an autotransformer to a lighting load to reduce the voltage delivered to the load and to thereby reduce the power consumed by the load.
The prior art concepts which utilize an autotransformer and a switching means for either selectively applying one or more taps of the transformer to the load or shorting portions of the autotransformer for controlling the voltage applied to the load, do indeed serve the aforementioned purpose of reducing power consumption in a lighting load but unfortunately suffer from a number of disadvantages which the present invention is designed to overcome. By way of example, in such prior art disclosures, the switch unit that is used to control the voltage applied to the load, is normally interposed between the input power and the load. As a result, it must be capable of supporting the entire load current on either the input or output terminals of the autotransformer. Accordingly, to withstand such high carrying current requirements, such switching devices must be large and bulky and are commensurately expensive. The high cost of such units tends to defeat the cost saving aspect of power consumption reduction thereby reducing the consumer's motivation for employing such power reduction systems in the first place.
A number of other patents that disclose the use of relay-controlled transformer windings include the following:
U.S. Pat. No. 2,180,193--Brand PA1 U.S. Pat. No. 2,853,654--Swasey PA1 U.S. Pat. No. 3,652,824--Okada
Although these three additional prior art disclosures are not as relevant to the present invention as the two prior art disclosures previously discussed, it is to be noted that in each case the disclosure relates to a relay-controlled transformer mechanism in which at least one relay or equivalent switching device is interposed in the direct path between the input power and the output power to the load, thereby suffering the aforementioned disadvantages of the prior art.